Abstract: Ground closure rate between an aircraft and underlying terrain is obtained by differentially combining a radio altimeter derived rate signal and a barometric altitude rate signal to obtain a rate of change of ground profile signal. The ground profile rate is filtered on an autocorrelation basis to obtain a profile rate signal devoid of amplitude pulses introduced by sharp or discontinuous terrain features and recombined with barometric rate to obtain ground closure rate. The filtering technique imposes no rate limitation on the radio rate signal.

Abstract: A digital oscillator with output frequency accurately changeable from one period to the next. A plurality of retriggerable monostable multivibrators having discretely different design pulse widths are OR'd to an output monostable multivibrator having the narrowest design pulse width. The plurality of monostable multivibrators are triggered in common by the OR'd outputs thereof such that the longest pulse width one thereof defines the period of the output monostable multivibrator. Logic enabling means permit selection of multivibrator outputs to be OR'd.

Abstract: A method and means for obtaining a linear rate of change signal from an input analog signal whose magnitude exhibits a logarithmic amplitude variation over at least a portion of the range of the independent variable defining said signal. The nonlinear rate of change of the input signal is obtained by differentiation, and the resulting nonlinear rate signal is multiplied by the nonlinear function of the dependent variable defining the input signal, which function is implemented in accordance with that defined from a mathematical differentiation of the expression defining the nonlinear characteristic of the input signal.

Abstract: An automatic radio direction finding system employing an integrated antenna unit containing both sense and loop antennas in a single compact enclosure. Signal processing circuitries by means of which a low-frequency switching modulation is imposed on one of the antennas, as well as broad-band R-F preamplification and signal combining circuitry for the antenna outputs, are accomplished within the unit. The combining circuit output in the antenna unit, and the remote receiver input, have impedances matching that of a standard coaxial cable interconnect, such that the voltage dividing action effected by conventional antenna cable interconnect means is removed, permitting a small sense antenna of considerably less H.sub.e C.sub.a product to provide necessary sensitivity.

Abstract: A digital hysteresis circuit which generates delayed, clock-synchronous output pulses from input pulses having a random timing relationship with the clock. Input pulses slewing generally in or out on a repetitive clock defined time base may back up from the direction they are slewing by a predetermined time interval without changing the time position of the clock-synchronous, time-delayed output pulses which they successively generate. The circuit is useful in reducing jitter in the read-out of a digital counter while the counter is operating by preventing a load command pulse occurring at counter transition time from effecting a read-out at that instant, and further effective in reducing jitter in the commanded read out from a digital counter where system uncertainty might otherwise cause shift of successive input commands from their normally predictable time positions.

Abstract: A method and means for employing digital means to calibrate an analog sweep waveform in a range determining system. The method imparts digital accuracy in maintaining the voltage-distance analog of the sweep waveform by generating a clock defined strobe at a time when the sweep voltage should reach a reference voltage level, comparing at strobe time the sweep voltage with a precision voltage source of reference level, and correcting the slope of the sweep voltage in accordance with any discrepancy existing at the time of comparison.

Abstract: A fast search system for DME generates range gates at the time an analog sweep voltage rises to the magnitude of an analog integrator waveform, the latter having a slope less than that of the sweep voltage and provided with a constant current source input. The current source is selectively inhibited by digital control means responsive to the relative time occurrence of range gates and reply pulses such that the range gate occurs during an instant interrogation period at a point in time corresponding to a predetermined percentage of the time at which appeared the first received reply pulse in a preceding interrogation period.

Abstract: A drive mechanism for positioning a moveable indicator in rotation about, and/or radial displacement with respect to, a fixed reference index. Dual dial cord drives are employed which are driven from respective inputs definitive of the rotation and radial displacement to be individually or compositely imparted to the moveable indicator. The pair of dial cords are attached circumferentially to diametrically opposed portions of a cylinder with the moveable indicator extending on a diameter common to those portions. The cylinder portions are confined between, and maintained in sliding tangential engagement with, respective ones of a pair of space-separated, fixed-mounted channel guides. Implementations of the cylinder portions are exampled as diametrically opposed segments of a cylinder, diametrically opposed points on a ring, and diametrically opposed circumferential extremes of a cylindrical plate.